Grouting Methane Drainage Holes in Coalbeds.
Proc Asce Spec Conf in Geotech Engr New Orleans Louisiana 1982 Feb; :651-664
Horizontal drainage holes drilled into gassy coalbeds are effective in reducing methane flows into mine workings during mining operations. Drainage holes were drilled 415 to 2,126 ft (126 to 648 m) long. Holes were sealed with cement before interception by the mining machine to avoid formation of explosive methane-air mixtures. The cement slurry consisted of cement, fly ash, and fluidifier. Excess water was used in the slurry to avoid plugging problems because of the distance the slurry was pumped. When the hole was filled with slurry, pressure was increased to squeeze excess water into the coalbed fracture system. Examination of intercepted drainage holes showed that in some cases, water had separated from the slurry and had not been squeezed into the fracture system. In no case was cement slurry forced into the fracture system. In a subsequent study, water content of the slurry was reduced to recommended quantitites. Where water flow from drainage holes before grouting was less than 0.5 Gal/min (1.9 L/min), holes were satisfactorily sealed. Water flow greater than 2 gal/min (7.6 L/min) before grouting diluted the slurry and water stratified in the hole.
Proc. Asce Spec. Conf. in Geotech. Engr., New Orleans, Louisiana, Feb. 10- 12, 1982, PP. 651-664